Suspended ceilings, sometimes also known as false ceilings, are very common features of commercial, retail and many other buildings. A suspended ceiling is formed of a grid that is suspended from a permanent ceiling or structure and ceiling tiles supported by the grid. The suspended ceiling grid is formed of a series of beam structures having a cross-section in the shape of an inverted T, i.e., having a vertical rib and two horizontal flanges extending from the bottom of the vertical rib along the length of the beam. Hereinafter these grid pieces will be referred to as T-bars. The T-bars forming the suspended ceiling grid are suspended from the permanent ceiling above via wires or other structures. (Along the walls of a room in which a suspended ceiling is installed the beam structures employed have an L-shaped cross section, i.e., having a vertical rib portion that is attached to the wall and a horizontal flange portion extending from the vertical rib portion along the length thereof into the room.) The T-bars forming the suspended ceiling are laid out to define a grid of square or rectangular openings between the T-bars. The openings typically are 2 feet by 2 feet square or 2 feet by 4 feet in size (although other sized openings also may be defined). Ceiling tiles of the appropriate size are placed in the openings and supported along their edges by the horizontal flanges of the T-bars forming the suspended ceiling grid to complete the suspended ceiling. The ceiling tiles, also known as acoustical tiles, typically are made of a generally sound and heat insulating material, such as foam or the like, with a lower surface, that is visible to those in the room below the ceiling, decoratively formed. The space between the suspended ceiling thus formed by the T-bar grid and ceiling tiles and the permanent ceiling structure forms a convenient space for running various utilities, such as heating, ventilation and air conditioning ducts, electrical wiring, etc. The suspended ceiling hides these utilities from view while also allowing access thereto, by removing ceiling tiles and/or pieces of the T-bar grid from the suspended ceiling, for servicing when necessary.
Besides the ceiling tiles, the suspended ceiling grid also is used to support various other structures and devices, such as lighting fixtures, heating, ventilation and air conditioning vents, fire and smoke alarms, motion detectors, etc. These structures and devices may be attached to and/or supported by the suspended ceiling grid so as to extend at least partially below the suspended ceiling into the room below or may be entirely recessed above the plane of the suspended ceiling grid. Electrical and other connections for such structures and devices typically are formed in the space between the suspended ceiling and the permanent ceiling structure from which it is suspended so as not to be visible in the room below.
Perhaps the most common structures and devices, other than ceiling tiles, to be supported by a suspended ceiling grid are lighting fixtures. Over the years many different types of lighting fixtures have been developed for use in suspended ceilings and many structures and methods have been developed for attaching such fixtures to the suspended ceiling T-bar grid. A typical lighting fixture for use in a suspended ceiling includes a box like structure, sometimes called a troffer, having end and side walls, a top reflector closing one end of the end and side walls, and an open side opposite the top reflector. Lamps, such as fluorescent lamps, typically may be mounted within or suspended from the fixture box. Often the open side of the fixture box may be covered by a hinged or otherwise removable lens or louver, that disburses the light from the lamps but that can be easily removed to replace the lamps when necessary. Electrical connections for the fixture, including, typically, the fluorescent lamp ballast, typically are provided on the top of the top reflector, so as not to be visible from below when the lighting fixture is installed in a suspended ceiling.
Lighting fixtures of the type described typically are sized and designed such that they may be supported in the openings in a suspended ceiling grid along the bottom edges of the end and side walls thereof that are placed on the horizontal flanges of the T-bars surrounding the opening. Clamps or other structures often are used to secure the lighting fixture in position to the ceiling grid T-bars. Actually placing the lighting fixture in position within the T-bar grid can, however, prove to be a challenge. If the installer has access from above the suspended ceiling he can lower the lighting fixture into position on the T-bar grid from above. This, however, rarely is the case, as the space between the suspended ceiling grid and the permanent ceiling structure above typically does not provide enough room or access to allow the lighting fixture to be lowered into the suspended ceiling grid from above. The other option is to lift the lighting fixture into position from below. However, manipulating a lighting fixture that is several feet across through a suspended ceiling grid and into position from below is very cumbersome and often difficult.
One common solution to the problem of installing a lighting fixture as a substantially single piece in a suspended ceiling has been to provide a lighting fixture in several pieces that are assembled in position in the suspended ceiling to form the lighting fixture. Individual smaller pieces forming the lighting fixture are more easily moved into position in the suspended ceiling grid from below than an entire lighting fixture several feet across. Many such lighting fixtures that may be assembled in place in a suspended ceiling grid in this manner have been developed. However, none of the known solutions has proved entirely successful. Most such solutions require that many lighting fixture pieces be assembled together in a suspended ceiling grid using various fasteners and tools. As anyone who has done so can testify, manipulating many pieces, fasteners and tools while working over one's head is difficult, uncomfortable, and time consuming.
What is desired, therefore, is an improved lighting fixture for a suspended ceiling that can be mounted in a suspended ceiling from below the ceiling easily and quickly. Preferably, the lighting fixture can be assembled from a minimal number of pieces that can be installed in place in a suspended ceiling grid without requiring the manipulation of tools or fasteners.